CORN IN ROTATION 93 



116. Acre Value. The average annual value of an acre 

 of corn for the United States for the five years from 1912 

 to 1916 was $16.94, but in 1917 it was $33.85. The highest 

 value is shown in the North Atlantic states, the Far Western 

 and the South Central states ranking next in order. The 

 average acre value in Illinois for the five years from 1912 

 to 1916 was $19.06 and in Iowa, $20.17. In 1917 the acre 

 values in these two states were $41.80 and $39.96, respectively. 

 The highest acre value in 1917 was in Connecticut, $109.65; 

 the lowest, in Oklahoma, $12.50. This low acre value was 

 due to low average yield, 8.5 bushels, caused by drought. 



CORN IN CROP ROTATIONS 



117. Corn Decreases Fertility. It is well known that 

 if a piece of land that has been cropped to grain for a number 

 of years is planted to corn and cultivated well, better crops 

 of grain will be produced on the field the following year or 

 years. This has led to the belief that corn is a soil-building 

 crop. Tests conducted at many experiment stations where 

 corn has been grown on the same plat continuously for a 

 number of years without fertilizer show that the produc- 

 tivity of the plats has gradually decreased until very poor 

 yields result. In fact, these experiments show that the 

 productivity of the soil is more rapidly decreased by corn 

 than by grain crops. These two facts seem somewhat con- 

 trary, but when studied prove to be just what might rea- 

 sonably be expected. 



118. Cultivation Liberates Plant Food. As stated else- 

 where, plant food is made solul)le or available for plants very 

 largely by the decomposition of vegetable matter. Vege- 

 table matter can decompose or rot only when in the pres- 

 ence of air and moisture. Hay in the mow does not rot, 

 because it is kept dry. Silage in the silo does not rot, be- 

 cause ail is kept away from it. Vegetable matter in the soil, 

 that is, manure and roots and stems of plants, will naturally 



